1. Field of the Invention
The invention relates to methods for the collection, clotting and separation of the light, liquid portion of blood from the heavy, substantially cellular portion of blood and more particularly relates to a method of maintaining the blood clot activating property of a clot activator employed in such method.
2. Brief Description of the Prior Art
The length of time required for blood collected in a blood collection assembly to clot after its removal from the mammalian body is dependent upon a number of interrelated, little understood factors. The time taken to form a blood clot in collected blood is dependent to some extent on the rate of conversion of prothrombin to thrombin and of fibrinogen to fibrin. One of the factors which increases the rate of clot formation is exposure of the blood to "siliceous" materials such as glass, silica, kaolin, bentonite, siliceous aluminum hydrate and diatomaceous earth or kieselguhr; see for example Soulier et al, British Journal of Haemetology, Vol. 6, pages 88 through 101 (1960).
Recently, blood collection assemblies for the separation of blood into its light liquid and heavy, substantially cellular phases have been proposed which include gel-like silicone compositions having a density intermediate between the light, liquid phase and the heavy, substantially cellular phase of blood. These gel materials are placed in the container component of a blood collection system and sealed therein for subsequent use as a barrier between the blood phases; see for example U.S. Pat. Nos. 3,852,194; 3,852,194; 3,920,549; and 3,997,442. In addition, it has also been proposed to add particles of siliceous materials to the container component of the blood collection system; see for example French Pat. No. 2,290,665.
In general, the prior art methods and apparatus are not totally satisfactory for the collection of blood and its subsequent separation into light, liquid phases and heavy, substantially cellular phases. The difficulty arises in that over a period of time the silicone based barrier gels give rise to vapors and spreading liquid films. The vapors eventually condense on the glass walls of the container and/or on the surfaces of the clot activator particles. The condensed vapors and the liquid films form a barrier on the activator surfaces as well as on the glass container walls. Subsequently, when blood is introduced into the container, it is prevented from contacting the activator particle surfaces and/or the glass container walls. Thus, one of the factors which promotes the enzymatic conversion of clot forming materials to blood clots is prevented from functioning.
By the method of my invention, the blood clot activating properties of the glass and/or activator particles is maintained during storage even over relatively long periods. When the blood is introduced into the blood container, the container glass wall and/or activator particles become available for contact with the blood to promote clot formation.